Since the development of the resist for a KrF excimer laser (248 nm), a pattern forming method based on chemical amplification has been employed as a resist pattern forming method in order to compensate for any sensitivity decrease caused by light absorption. A positive pattern forming method based on chemical amplification will be described by way of example. In this pattern forming method, an acid generator contained in exposed areas is decomposed upon exposure to light, such as an excimer laser, electron beams or an extreme ultraviolet light, to thereby generate an acid. In the stage of the bake after the exposure (Post-Exposure Bake: PEB), the generated acid is utilized as a reaction catalyst so that alkali-insoluble groups are converted to alkali-soluble groups. Thereafter, the exposed areas are removed by an alkali developer.
For use in the above method, various alkali developers have been proposed. For example, an aqueous alkali developer containing 2.38 mass % TMAH (aqueous solution of tetramethylammonium hydroxide) is universally used.
Moreover, the shortening of the wavelength of exposure light sources and the realization of high numerical apertures (high NA) for projector lenses have been advanced in order to cope with the miniaturization of semiconductor elements. Until now, an exposure unit using an ArF excimer laser of 193 nm wavelength as a light source has been developed. Further, a method, known as a liquid-immersion method, in which the space between a projector lens and a sample is filled with a liquid of high refractive index (hereinafter also referred to as an “immersion liquid”) has been proposed as a technology for enhancing the resolving power. Furthermore, an EUV lithography or the like in which exposure is carried out using an ultraviolet of further shorter wavelength (13.5 nm) has been proposed.
In another aspect, with respect to resist compositions, not only the currently mainstream positive resists but also negative resist compositions for use in the pattern formation by alkali development are being developed (see, for example, patent references 1 to 4). This reflects the situation in which in the production of semiconductor elements and the like, while there is a demand for the formation of a pattern with various configurations, such as a line, a trench and a hole, there exist patterns whose formation is difficult with the use of current positive resists.
Further, a pattern forming method using a negative developer, namely, a developer containing an organic solvent (hereinafter also referred to as an “organic solvent based developer”) is being developed. For example, patent reference 5 discloses a pattern forming method comprising the operations of applying onto a substrate a resist composition that when exposed to actinic rays or radiation, increases its solubility in a positive developer, namely, an alkali developer and decreases its solubility in a negative developer, exposing the applied resist composition to light and developing the exposed resist composition using a negative developer. This method realizes the stable formation of a high-precision fine pattern.
Still further, in recent years, the technology of using a specified rinse liquid in the stage of rinsing a resist film after development with respect to the pattern forming method using an organic solvent based developer is being developed (see, for example, patent reference 6). This technology realizes the inhibition of defects, such as residue-related defects and blob defects.